Seal for rotary concrete mixing drums



June 28, 1938. J. P. FABER SEAL FOR'ROTARY CONCRETE MIXING DRUMS Filed Dec. 24,, 1935 7:, IN VEN TOR.

ATTORNEY.

Patented June 28, 1938 UHTED STATES PATET QFFIQE SEAL FOR ROTARY CONCRETE MIXING DRUMS John P. Faber, Dunellen, N. J., assignor to Bansome Concrete Machinery Company, Plain- 5 Claims.

The improvements relate to means for pro viding a substantially liquid-tight seal or packing between a rotating member and a stationary part, and more particularly to a seal of this character between the fixed feed chute or hopper and the feed opening of a rotating concrete mixing drum. They may however be used in connection with the discharge chute and opening if desired. and for any other purpose to which they are adaptable.

In modern concrete mixing it has been found advantageous to seal the feed or charging opening of the drum to prevent the wet aggregates or soup from splashing out as the aggregates are raised by the mixing buckets or blades, dropped from the upper part of the drum and more or less violently agitated and moved about in different directions, to produce a thorough and uniform commingling of all the aggregates. But as the drum rotates quite rapidly and the feed chute which extends through the mouth or feed opening of the drum must be mounted in fixed position to receive and deliver into the drum the unmixed aggregates, the problem of providing an effective and durable liquid-tight seal between the two has been a serious one, on account of the relatively large diameter of the chute and the opening, the vibration caused by the rotation of the drum with its heavy load and the dumping of the unmixed aggregates into the chute in large batches, and the extremely gritty character of the small aggregates in the liquid portion of the mixture which are principally hard sand and minute fragments of rock mixed with cement and water.

Various attempts have been made to provide a seal of this character which will be effective at all times and underall conditions and will be sufficiently durable in use to keep the cost for upkeep and replacement within reasonable limits, but so far as I am aware no solution of this problem has heretofore been devised. Seals which are initially fairly satisfactory have been made at a cost comparable with the cost of the present seal, but as their life is very short, the cost as high as sixty dollars for a one yard machine and the labor and delay involved in replacement a serious item they have not been found satisfactory. Nor have such devices been so designed as to provide a tight seal under all conditions of use, as where the mixing drum is carrying an overload of the usual wet mixture bringing the level of such mixture when at rest up to or above the lower edge of the opening.

To overcome the difilculties above indicated and provide an efiective and durable seal, the

present improvements employ, in the illustrated preferred embodiment, an annulus of sheet or thin cast metal secured to the external periphery of the cylindrical discharge end of the feed chute and projecting therefrom in vertical plane to form a flange throughout the circumference of the chute, and the feed opening is provided with a pair of spaced rings of rubber or other suitable compressible and resilient material extending around its edge and projecting inwardly therefrom, and receiving snugly between them the annulus. As the charge opening and the said flange of the chute are both annular and are concentric and the compressible rings are formed on aligned radii the seal is maintained at all times and. is not affected by the rotation of the drum, which rotation is on a horizontal axis running through the centers on which the annular flange, the said rings and the edges of the opening are drawn. The pair of compressible rings is secured to the head of the drum around the opening by being clamped against the inner and outer faces of said head immediately adjacent to and surrounding the said opening, one ring being on the outer face and the other on the inner face thereof, and the rings extend beyond the edge of the opening and toward the chute a short distance to provide contact surfaces between them and the annular flange sufficient to form an eiiective seal. This extension of the flexible rings also provides fora certain degree of flexibility to compensate for vibration and the slight lateral movements of the drum in rotating or due to other causes. The flexible rings are clamped to the head of the drum at the edge of the opening by means of fiat annular metal plates one on the outer side of the outer ring and the other on the inner side of the inner ring with bolts at intervals passing through the said ring and plates and through holes in the drum head, one or both of the said plates preferably extending to the edges of their respective rings or in proximity thereto to reinforce and protect them and preserve their shape. The interposition of the rings however between the plates at their points of securement gives the latter a slight degree of flexibility in addition to the'flexibility of the relatively thin metal of which they are made.

The objects and advantages of the improvements will be apparent from the foregoing, and from the following description and accompanying drawing which describe and illustrate an exemplary embodiment thereof.

In the said drawing, Fig. l is a vertical medial cross section taken longitudinally through the head of a concrete mixing drum and feed chute embodying the improvements;

Fig. 2 is an end elevation thereof, with part of the chute broken away; and

Fig. 3 is an enlarged detail in section similar to that of Fig. l of certain parts.

In the said drawing l is the feed chute, 2 the head of the drum, 3 the annular sealing flange on the chute, 4a, the pair of rubber sealing rings, 5 the outside and 6 the inside metal c1amping ring, 7 one of the securing bolts for the rings and their reinforcing plates and 8 a union for a water pipe leading to the chute through the mouth 9, through which water is discharged into the drum for the batches of solid aggregates.

The bolts 1 are located at short intervals around the edge of the feed opening, and have their heads on the inner side of the plate 6- which should be made in two semi-circular sections for insertion and removal through the openingextend through the plate 5, compressible ring 4, drum head 2, compressible ring 4a and plate 5 and beyond the last named plate, the outer end of each bolt being threaded to receive a nut la, and a spring nut lock lb being located between the said nut and the plate 5 on the bolt. The plates 5 and E extend approximately to the inner edges of the compressible rings, but I prefer to have the rings extend slightly beyond the plates so that there will be less wear on their extreme inner edges, and small gritty particles of aggregates will be swept away from the flange 3 thereby and permitted to fall when the portion of the rings on which they have lodged reach a position above the middle of the opening. The space between the compressible rings is slightly greater than the thickness of the flange 3, this being provided for by having the flange slightly less in thickness than the head of the drum 2. Thus the head of the drum in practice is about /;th inch inthickness while the flange is ths. The plates 5 and 6 are of about the same gauge as the flange, and are of spring metal, so that they have a slight degree of flexibility. This flexibility, however, is increased, and the entire extending portion of the compressible packing rings and their plates is permitted to move or flex to the desired extent by the fact that the rings of compressible material are between the plates 5 and 6 and the drum head 2.

Adjustment for the wear of the rings 5 and 6 due to friction between them and the flange 3 is provided by the means of attaching them to the drum head, and especially the spring nut lock lb. When a new packing or seal is applied to the head of the drum and secured by the screw bolts '1, the pressure of the plates 5 and 6 will cause the compressible material of the rings 4 and la to be compressed to some extent between the plates and the head 2. This permits the said plates to approach each other slightly and narrow the space between the extending portions of the packing rings, which is not compressed, and thus establish a snug relation between the rings and the flange 3. The exact desired tightness of the seal can thus be attained by regulating the pressure of the nuts la. At the same time a further slight yielding of the plates is provided for by the spring nut locks lb. These nut locks permit the user to tighten up the packing when it is worn down by friction between it and the flange 3 by turning up the nuts, as Well as providing a certain yielding of the entire packing to compensate for vibration and slight movement of the drum and feed chute, it being apparent that when the portions of the rings which lap the head are compressed, the extending portions will be brought closer together, so that a satisfactory seal can be maintained in spite of considerable Wear, and the life of the packing thus prolonged.

While the construction and arrangement herein described and shown is the best mode in which I have contemplated applying the principle of the invention, it will be apparent that it may be modified in various ways and applied to or combined with other devices, without departing from that principle.

What I claim is:

l. A seal for the head of a rotatable drum for mixing concrete having a central opening therein and a non-rotating chute extending therethrough, comprising an annular flange on the chute, a plurality of packing rings of elastic material mounted on said head and extending beyond the edges of said opening spaced apart and providing a space between them for the reception of said flange corresponding substantially to the thickness of said flange and metallic reenforcing members for said rings mounted in close contact therewith, means for constantly pressing said members against said rings, one of said members being on the 'outer side of each ring and also extending therewith beyond the edges of the opening, said members overlapping said flange.

2. A seal for the head of a rotatable drum for mixing concrete having a central opening therein and a non-rotating chute extending therethrough, comprising an annular flange on said chute, a plurality of packing rings of elastic material mounted on said head and extending beyond the same over said opening spaced apart and providing a space between them corresponding substantially to the thickness of said flange and metallic reenforcing members for said rings mounted in close contact therewith, means for constantly pressing said members against said rings beyond the edges of the opening, and means for securing said rings adjustably and removably to said head at least one of said members overlapping said flange.

3. A seal for the head of a rotatable drum for mixing concrete having a central opening therein and a non-rotating chute extending therethrough, comprising an annular flange on the chute, a plurality of packing rings of elastic material mounted one on each side of said head and extending beyond the edges of said opening spaced apart and providing a space between them for the reception of and corresponding substantially to the thickness of said flange and a metallic clamping and reenforcing member for said rings mounted therewith and extending therewith over said flange, means for removably securing said rings and reinforcing member to said head, and a spring device for pressing said rings associated with said securing means and having locking engagement therewith.

4. A seal for the sheet metal head of a rotatable drum for mixing concrete, having a central opening therein and a non-rotating chute extending through said opening, comprising an annular flange on the chute, a plurality of packing rings of elastic material mounted one on each side of the head adjacent to and extending beyond the edges of said opening, so that said rings are spaced apart by said head and provide an annular space between them in which the outer part of said flange is received, means for compressing said rings against said head and thereby causing their said extending portions to approach each other and reduce the space in which the flange is received, to take up wear or make a closer seal between said parts, said means including relatively rigid members secured to said head and extending inwardly beyond the edges of said opening over a major portion of and in contact with said rings, a portion of said rings being free to move laterally to compensate for lateral movement of the flange without disconnecting them.

'5. In a device of the character described, a sheet metal head having a central opening, an elastic packing ring secured near the edges of the opening and extending well beyond the same and clear of said head, a reinforcing plate also secured near the edges of the opening and extending beyondthe same with said packing ring, a chute extending through said opening but spaced from the edges thereof, an annular flange on said chute in plane with the head, said packing ring and reinforcing plate overlapping said flange, and means for securing said ring and plate to the head, causing pressure upon said ring beyond the edges of the opening to press it against said flange, maintain a seal between said ring and flange and take up wear, comprising a bolt extending through the ring, head and plate, a head on said bolt and a spring on said bolt between the head and the plate constantly pressing the extending portion of said plate against said ring.

JOHN P. FABER. 

